Axle Assembly Having a Gear Reduction Unit and an Interaxle Differential Unit

ABSTRACT

An axle assembly having a gear reduction unit and an interaxle differential unit. The gear reduction unit may be operatively connected to an input shaft and may selectively provide gear reduction to a differential assembly and the interaxle differential unit. The interaxle differential unit may operatively connect the gear reduction unit to the output shaft.

TECHNICAL FIELD

This disclosure relates to an axle assembly that has a gear reductionunit that is operatively connected to an interaxle differential unit.

BACKGROUND

An axle assembly having an inter-axle differential is disclosed in PCTInternational Patent Publication No. WO 2004/009392.

SUMMARY

In at least one embodiment, an axle assembly is provided. The axleassembly may include a housing assembly, an input shaft, a gearreduction unit, a first coupling, and an interaxle differential unit.The housing assembly may receive a differential assembly. The inputshaft may be rotatable about a first axis and may be at least partiallyreceived in the housing assembly. The gear reduction unit may bedisposed in the housing assembly and may be operatively connected to theinput shaft. The gear reduction unit may include a planetary gear set.The planetary gear set may have a sun gear, a planet carrier, at leastone planet pinion, and a ring gear. The sun gear may be rotatable aboutthe first axis. The planet carrier may rotatably support a planetpinion. The ring gear may be fixedly positioned with respect to thehousing assembly. The first coupling may be movable between a firstposition and a second position. The first coupling may couple the inputshaft to the sun gear such that the sun gear and the input shaft arerotatable together about the first axis when in the first position. Thefirst coupling may couple the input shaft to the planet carrier suchthat the planet carrier and the input shaft are rotatable together aboutthe first axis when in the second position. The interaxle differentialunit that is received in a case that may be at least partially receivedin the planet carrier. The interaxle differential unit may operativelyconnect the planetary gear set to the differential assembly and to anoutput shaft.

In at least one embodiment, an axle assembly is provided. The axleassembly may include a housing assembly, an input shaft, a gearreduction unit, and an interaxle differential unit. The housing assemblymay receive a differential assembly. The input shaft may be at leastpartially received in the housing assembly and may be rotatable aboutthe first axis. The gear reduction unit may be operatively connected tothe input shaft. The gear reduction unit may include a planetary gearset. The planetary gear set may include a sun gear, a planetary ringgear, a planet carrier, and at least one planet pinion. The sun gear andthe planetary ring gear may be rotatable about the first axis. Theplanet carrier may rotatably support a planet pinion that may be inmeshing engagement with the sun gear and the planetary ring gear. Theplanetary ring gear may be movable between a first position and a secondposition. The planetary ring gear may be coupled to the housing assemblysuch that the planetary ring gear does not rotate about the first axiswhen in the first position. The planetary ring gear may be coupled tothe planet carrier such that the planet carrier and the planetary ringgear are rotatable together about the first axis when in the secondposition. The interaxle differential unit may be at least partiallyreceived in the planet carrier and may operatively connect the planetarygear set to the differential assembly and to an output shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an axle assembly having a differentialcarrier that supports a differential assembly.

FIG. 2 is a section view along section line 2-2 showing a firstembodiment that includes a gear reduction unit, a first coupling in afirst position, and an interaxle differential unit in an unlockedcondition.

FIG. 3 is a magnified section view of a portion of the differentialcarrier of FIG. 2 with the first coupling in a second position and theinteraxle differential unit in a locked condition.

FIGS. 4 and 5 are exploded views of a portion of the differentialcarrier.

FIGS. 6 and 7 are section views of a second embodiment that includes agear reduction unit having a planetary gear set and illustrates a firstcoupling in first and second positions, respectively.

FIGS. 8 and 9 are section views of a third embodiment that includes agear reduction unit having a planetary gear set and illustrates aplanetary ring gear in first and second positions, respectively.

FIGS. 10 and 11 are section views of a fourth embodiment that includes agear reduction unit having a planetary gear set and illustrates aplanetary ring gear in first and second positions, respectively.

FIG. 12 is a section view of another axle assembly configuration thatincludes a gear reduction unit, a first coupling in a first position,and an interaxle differential unit in an unlocked condition.

FIG. 13 is a section view of the axle assembly of FIG. 12 with the firstcoupling in a second position and the interaxle differential unit in alocked condition.

FIGS. 14-16 are section views of an embodiment that includes a gearreduction unit having a planetary gear set and illustrates a firstcoupling in neutral, first and second positions, respectively.

FIGS. 17-19 are section views of an embodiment that includes a gearreduction unit having a planetary gear set and illustrates a firstcoupling in neutral, first and second positions, respectively.

FIGS. 20-22 are section views of an embodiment that includes a gearreduction unit having a planetary gear set and illustrates a firstcoupling in neutral, first and second positions, respectively.

FIGS. 23-25 are section views of an embodiment that includes a gearreduction unit having a planetary gear set and illustrates a firstcoupling in neutral, first and second positions, respectively.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring to FIG. 1, an example of an axle assembly 10 is shown. Theaxle assembly 10 may be provided with a motor vehicle like a truck, bus,farm equipment, mining equipment, military transport or weaponryvehicle, or cargo loading equipment for land, air, or marine vessels.The motor vehicle may include a trailer for transporting cargo in one ormore embodiments.

The axle assembly 10 may be part of a vehicle drivetrain that mayprovide torque to one or more traction wheel assemblies that may includea tire mounted on a wheel. One or more axle assemblies may be providedwith the vehicle. For example, the axle assembly 10 may be part of atandem axle configuration or multi-axle configuration that may include aplurality of axle assemblies that may be connected in series. As is bestshown with reference to FIGS. 1 and 2, the axle assembly 10 may includea housing assembly 20, a case 22, a gear reduction unit 24, an interaxledifferential unit 26, a differential assembly 28, and at least one axleshaft 30.

Referring to FIG. 1, the housing assembly 20 may receive variouscomponents of the axle assembly 10. In addition, the housing assembly 20may facilitate mounting of the axle assembly 10 to the vehicle. Thehousing assembly 20 may include an axle housing 40 and a differentialcarrier 42.

The axle housing 40 may receive and support the axle shafts 30. In atleast one embodiment, the axle housing 40 may include a center portion50 and at least one arm portion 52.

The center portion 50 may be disposed proximate the center of the axlehousing 40. The center portion 50 may define a cavity that may receivethe differential assembly 28. A lower region of the center portion 50may at least partially define a sump portion that may contain lubricant.Splashed lubricant may flow down the sides of the center portion 50 andmay flow over internal components of the axle assembly 10 and gather inthe sump portion.

The center portion 50 may include a carrier mounting surface. Thecarrier mounting surface may face toward and may engage the differentialcarrier 42. The carrier mounting surface may facilitate mounting of thedifferential carrier 42 to the axle housing 40. For example, the carriermounting surface may have a set of holes that may be aligned withcorresponding holes on the differential carrier 42. Each hole mayreceive a fastener, such as a bolt, that may couple the differentialcarrier 42 to the axle housing 40.

One or more arm portions 52 may extend from the center portion 50. Forexample, two arm portions 52 may extend in opposite directions from thecenter portion 50 and away from the differential assembly 28. The armportions 52 may have substantially similar configurations. For example,the arm portions 52 may each have a hollow configuration or tubularconfiguration that may extend around the corresponding axle shaft 30 andmay help separate or isolate the axle shaft 30 from the surroundingenvironment. An arm portion 52 or a portion thereof may be integrallyformed with the center portion 50. Alternatively, an arm portion 52 maybe separate from the center portion 50. In such a configuration, eacharm portion 52 may be attached to the center portion 50 in any suitablemanner, such as by welding or with one or more fasteners. Each armportion 52 may define an arm cavity that may receive a correspondingaxle shaft 30.

Referring to FIGS. 1 and 2, the differential carrier 42, which may alsobe called a carrier housing, may be mounted on the center portion 50 ofthe axle housing 40. The differential carrier 42 may receive the case22, the gear reduction unit 24, and the interaxle differential unit 26and may support the differential assembly 28. The differential carrier42 may be configured as a single component or as multiple componentsthat are assembled to each other. For instance, the differential carrier42 may include a first portion that is mounted to the axle housing 40and a second portion that is mounted to the first portion that mayreceive the interaxle differential unit 26. An end of the differentialcarrier 42 disposed opposite the axle housing 40 could include or beconfigured as a removable cover. As is best shown with reference toFIGS. 2 and 3, the differential carrier 42 may have one or more bearingsupports 54 and a housing face gear 56.

Referring to FIG. 2, the bearing support 54 may support a roller bearingassembly 60 that may rotatably support the differential assembly 28. Forexample, two bearing supports 54 may be received in the center portion50 and may be located proximate opposite sides of the differentialassembly 28. The bearing support 54 may be provided in variousconfigurations. For example, a bearing support 54 may include a pair oflegs that extend from the differential carrier 42. A bearing cap may bemounted to the legs and may arch over a roller bearing assembly 60. Insuch a configuration, the bearing support 54 and bearing cap maycooperate to extend around, receive, and secure the roller bearingassembly 60. As another example, the bearing support 54 may be receivedin a roller bearing assembly 60 which in turn may support thedifferential assembly 28.

Referring to FIG. 3, the housing face gear 56 may include a set of teeththat may face toward the case 22. The set of teeth may be selectivelyengaged by a first coupling as will be discussed in more detail below.

Referring to FIGS. 1-4, additional components that may be associatedwith transmitting torque to or through the axle assembly 10 may includean input yoke 70, an input shaft 72, a drive pinion 74, an output shaft76, and an output yoke 78.

Referring to FIG. 1, the input yoke 70 may facilitate coupling of theaxle assembly 10 to a torque source. For example, the input yoke 70 maybe coupled to the drive shaft. The input yoke 70 may be coupled to theinput shaft 72, the input shaft 72 being best shown in FIG. 2. Forexample, the input yoke 70 may have an opening that receives the inputshaft 72 and may be secured to the input shaft 72 with a nut.

Referring to FIGS. 2 and 3, the input shaft 72 may extend along and maybe configured to rotate about a first axis 80. For example, the inputshaft 72 may be rotatably supported by one or more roller bearingassemblies 90 that may be disposed on the differential carrier 42, thedrive pinion 74, or both. The input shaft 72 may be operativelyconnected to the gear reduction unit 24 as will be discussed in moredetail below.

Referring to FIG. 2, the drive pinion 74 may provide torque to a ringgear 100 that may be provided with the differential assembly 28. Thedrive pinion 74 may extend along and may be configured to rotate about afirst axis 80. The ring gear 100 may rotate about a second axis 82. Thedrive pinion 74 may be coaxially disposed with the output shaft 76 andmay be spaced apart from the input shaft 72 and the output shaft 76. Thedrive pinion 74 may be rotatably supported by one or more roller bearingassemblies 102 that may be disposed on the differential carrier 42, theinput shaft 72, or both. A preload nut 104 may be threaded onto thedrive pinion 74 and may be rotated to exert a desired preload force onthe roller bearing assemblies 102. In at least one embodiment, the drivepinion 74 may include a shaft portion 110 and a gear portion 112.

Referring to FIGS. 2 and 4, the shaft portion 110 may extend from theinteraxle differential unit 26 to the gear portion 112. As is best shownwith reference to FIG. 4, the shaft portion 110 may include an innerdrive pinion surface 120, a drive pinion passage 122, a drive pinionouter surface 124, and a drive pinion spline 126.

The inner drive pinion surface 120 may be spaced apart from the firstaxis 80 and may be radially disposed with respect to the first axis 80.For example, the inner drive pinion surface 120 may be an insidecircumference of the drive pinion 74. The inner drive pinion surface 120may be spaced apart from and may not engage the output shaft 76. Theinner drive pinion surface 120 may extend completely through the drivepinion 74 and may define the drive pinion passage 122.

The drive pinion passage 122 may extend along the first axis 80. Theoutput shaft 76 may extend through the drive pinion passage 122.

The drive pinion outer surface 124 may be disposed near an end of theshaft portion 110. In at least one embodiment, the drive pinion outersurface 124 may face away from the first axis 80 and may be an outsidecircumference of a portion of the shaft portion 110. The drive pinionouter surface 124 may optionally support a stabilizer bearing of theinteraxle differential unit 26.

The drive pinion spline 126 may be disposed opposite the drive pinionpassage 122. The drive pinion spline 126 may include a plurality ofteeth. The teeth may be disposed substantially parallel to the firstaxis 80 and may mate with a corresponding spline on a second side gearof the interaxle differential unit 26 as will be discussed in moredetail below.

The gear portion 112 may be disposed at an end of the shaft portion 110.The gear portion 112 may have a plurality of teeth that may mate withcorresponding teeth on the ring gear 100. The gear portion 112 may beintegrally formed with the shaft portion 110 or may be provided as aseparate component that may be fixedly disposed on the shaft portion110.

Referring to FIG. 2, the output shaft 76 may extend along and may beconfigured to rotate about the first axis 80. For instance, the outputshaft 76 may be supported by one or more roller bearings that may bedisposed on the housing assembly 20. The output shaft 76 may extendthrough the drive pinion 74 and the drive pinion passage 122. Inaddition, the output shaft 76 may extend through a spider of theinteraxle differential unit 26 as will be discussed in more detailbelow. The output shaft 76 may be coupled to the interaxle differentialunit 26 at a first end. For example, the output shaft 76 may be fixedlycoupled to a second side gear of the interaxle differential unit 26. Theoutput shaft 76 may be fixedly coupled to the output yoke 78 at a secondend that may be disposed opposite the first end.

Referring to FIG. 1, the output yoke 78 may facilitate coupling of theoutput shaft 76 to a second axle assembly that may be disposed in serieswith the axle assembly 10. For instance, the output yoke 78 may becoupled to a connecting shaft, such as a prop shaft, which in turn maybe operatively connected to the second axle assembly. As such, theoutput shaft 76 and the output yoke 78 may provide torque to the secondaxle assembly.

Referring to FIG. 2, the case 22 may be received in the housing assembly20. For example, the case 22 may be received in the differential carrier42 and may be rotatable about the first axis 80 with respect to thedifferential carrier 42. The case 22 may receive components of the gearreduction unit 24 and the interaxle differential unit 26. In addition,the case 22 may have a multipiece construction that may facilitateassembly or positioning of the gear reduction unit 24 and the interaxledifferential unit 26 inside the case 22. In the configuration shown, athree-piece case is depicted; however, it is contemplated that the case22 may have a greater or lesser number of pieces. In a three-piececonfiguration, the case 22 may include a first case portion 130, asecond case portion 132, and a third case portion 134 that may cooperateto define one or more cavities. For example, a single cavity may beprovided that may receive components of the gear reduction unit 24 andthe interaxle differential unit 26. In at least one other configuration,the case portions may define separate cavities that receive the gearreduction unit 24 and the interaxle differential unit 26. The caseportions may be fastened together in any suitable manner, such as withone or more fasteners like bolts.

Referring to FIGS. 2 and 5, the first case portion 130 may receive atleast a portion of the gear reduction unit 24. The first case portion130 may include a first case portion face gear 140.

The first case portion face gear 140 may be disposed at an end of thecase 22 that may face away from the interaxle differential unit 26. Asis best shown in FIG. 2, the first case portion face gear 140 mayinclude a plurality of teeth that may be arranged around the first axis80. The teeth may extend away from the first case portion 130 toward afirst coupling as will be described in more detail below.

The second case portion 132 may be disposed between and may be mountedto the first case portion 130 and the third case portion 134. The secondcase portion 132 may receive a portion of the gear reduction unit 24,the interaxle differential unit 26, or both. The second case portion 132may be configured as a ring that may extend around the first axis 80.

Referring to FIGS. 2 and 4, the third case portion 134 may be disposedopposite the first case portion 130. The third case portion 134 mayreceive at least a portion of the interaxle differential unit 26. Thethird case portion 134 may include a third case portion face gear 150.

Referring to FIG. 2, the third case portion face gear 150 may bedisposed at an end of the case 22 that may face toward the ring gear100. As is best shown in FIG. 2, the third case portion face gear 150may include a plurality of teeth that may be arranged around the firstaxis 80. The teeth may extend away from the third case portion 134toward a clutch collar as will be described in more detail below.

Referring to FIGS. 4 and 5, the first case portion 130 may cooperatewith the second case portion 132 to define one or more spider shaftholes 160. Similarly, the second case portion 132 may cooperate with thethird case portion 134 to define one or more spider shaft holes 162. Aspider shaft hole 160 may receive a shaft of a spider of the gearreduction unit 24. A spider shaft hole 162 may receive a shaft of aspider of the interaxle differential unit 26. In the configurationshown, three spider shaft holes 160, 162 are shown; however, it iscontemplated that a greater or lesser number of spider shaft holes 160,162 may be provided. The spider shaft holes 160, 162 may be spaced apartfrom each other and may be arranged around the first axis 80. Forexample, spider shaft holes 160, 162 may be disposed along axes that maybe disposed substantially perpendicular to the first axis 80.

Referring to FIG. 2, the gear reduction unit 24 may operatively connectthe input shaft 72 to the case 22. The gear reduction unit 24 mayprovide different drive gear ratios to the differential assembly 28 andto the output shaft 76 and another axle assembly connected in serieswith the axle assembly 10. For example, the gear reduction unit 24 mayprovide a first drive gear ratio and a second drive gear ratio. Thefirst drive gear ratio, which may be referred to as a low range drivegear ratio, may provide gear reduction from the input shaft 72 to thedrive pinion 74 (and hence to the axle shafts 30 of the axle assembly10) and the output shaft 76 (and hence to the axle shafts of a secondaxle assembly). For instance, the first drive gear ratio may provide a2:1 gear ratio or more. The first drive gear ratio may provide increasedtorque to a vehicle traction wheel as compared to the second drive gearratio. The second drive gear ratio, which may be referred to as a highrange drive gear ratio, may provide a different gear reduction ratio orlesser gear reduction ratio than the first drive gear ratio. Forinstance, the second drive gear ratio may provide a 1:1 gear ratio. Thesecond drive gear ratio may facilitate faster vehicle cruising or acruising gear ratio that may help improve fuel economy.

As is best shown with reference to FIGS. 2, 3 and 5, the gear reductionunit 24 may include an input gear 170, a first coupling 172, a firstside gear 174, a spider 176, and at least one pinion gear 178. The case22 may at least partially receive the input gear 170, first side gear174, spider 176, and pinion gear(s) 178.

Referring to FIG. 2, the input gear 170 may extend along and may beconfigured to rotate about the first axis 80. The input gear 170 may becoaxially disposed with the input shaft 72 and may be spaced apart fromthe input shaft 72. The input gear 170 may be rotatably supported by oneor more roller bearing assemblies 180 that may be disposed on thedifferential carrier 42. In FIG. 2, two roller bearing assemblies 180are shown that may be spaced apart from each other and may extend aroundthe input gear 170. In at least one embodiment, the input gear 170 mayinclude a shaft portion 190 and a gear portion 192.

Referring to FIGS. 2 and 5, the shaft portion 190 may be at leastpartially disposed outside the case 22 and may extend to the gearportion 192. The shaft portion 190 may at least partially define aninput pinion passage 194 through which the input shaft 72 may extend.One or more roller bearing assemblies 90 may be disposed in the inputpinion passage 194 and may rotatably support the input gear 170 upon theinput shaft 72. In addition, the shaft portion 190 may include an inputpinion spline 196. The input pinion spline 196 may be axially positionedbetween the gear portion 192 and an end of the shaft portion 190 that isdisposed opposite the gear portion 192. The input pinion spline 196 mayinclude a plurality of teeth. The teeth may be disposed substantiallyparallel to the first axis 80 and may mate with a corresponding splineon the first coupling 172.

The first coupling 172, which may also be referred to as a first collar,may be moveably disposed on the input gear 170. The first coupling 172may move axially or move along the first axis 80 between a firstposition and a second position as will be discussed in more detailbelow. As is best shown in FIG. 5, the first coupling 172 may begenerally ring-shaped and may include a coupling hole 200, a firstcoupling face gear 202, a second coupling face gear 204, and a couplinggroove 206.

The coupling hole 200 may extend through the first coupling 172 andextend around the first axis 80. The coupling hole 200 may receive theinput gear 170 as is best shown in FIG. 2. For example, the firstcoupling 172 may have a spline that may extend into the coupling hole200 and toward the first axis 80 and may mate with the input pinionspline 196. The mating splines may allow the first coupling 172 to movein an axial direction or along the first axis 80 while inhibitingrotation of the first coupling 172 about the first axis 80 with respectto the input gear 170.

The first coupling face gear 202 may include a set of teeth that mayface away from the case 22. The set of teeth may be arranged around thefirst axis 80 and may selectively engage the teeth of the housing facegear 56 of the differential carrier 42 depending on the position of thefirst coupling 172.

The second coupling face gear 204 may be disposed opposite the firstcoupling face gear 202. The second coupling face gear 204 may include aset of teeth that may face toward the case 22. The set of teeth may bearranged around the first axis 80 and may selectively engage the teethof the first case portion face gear 140 of the case 22 depending on theposition of the first coupling 172.

The coupling groove 206 may face away from the first axis 80 and mayextend around the first axis 80. The coupling groove 206 may receive alinkage, such as a shift fork, that may operatively connect the firstcoupling 172 to a first actuator 208. The first actuator 208 may movethe first coupling 172 between the first position and the secondposition. The first actuator 208 may be of any suitable type, such as amechanical, electromechanical, electrical, pneumatic, or hydraulicactuator. In addition, the first actuator 208 may move the firstcoupling 172 or any variants of the first coupling described below to aneutral position that may be disposed between the first position and thesecond position.

Referring to FIG. 2, the first coupling face gear 202 may engage thehousing face gear 56 and the second coupling face gear 204 may bedisengaged from the first case portion face gear 140 when the firstcoupling 172 is in the first position. As such, the input gear 170 maynot rotate about the first axis 80, but the case 22 may rotate about thefirst axis 80 with respect to the input gear 170. As a result, the inputshaft 72 and first side gear 174 may rotate together about the firstaxis 80 and the pinion gears 178 may rotate with respect to the spider176 and react against the stationary first side gear 174, therebyrotating the case 22.

Referring to FIG. 3, the first coupling face gear 202 may be disengagedfrom the housing face gear 56 and the second coupling face gear 204 maybe engaged with the first case portion face gear 140 when the firstcoupling 172 is in the second position. As such, the case 22 may notrotate about the first axis 80 with respect to the input gear 170, butthe case 22 and the input gear 170 may rotate together about the firstaxis 80. As a result, the input shaft 72 and first side gear 174 mayrotate together about the first axis 80, but the pinion gears 178 maynot rotate with respect to the spider 176 since the input gear 170 andspider 176 are both fixedly positioned with respect to the case 22.

Referring to FIGS. 2, 3 and 5, the first side gear 174 may be fixedlydisposed on the input shaft 72. For example, the first side gear 174 mayhave a center bore that may receive the input shaft 72. The center boremay include a spline that may mate with a corresponding spline on theinput shaft 72. As such, the first side gear 174 may not rotate aboutthe first axis 80 with respect to the input shaft 72.

The spider 176 may be fixedly positioned with respect to the case 22 andmay be rotatably disposed on the input shaft 72. In at least oneconfiguration, the spider 176 may include a spider hole 210 and one ormore spider shafts 212.

Referring to FIG. 5, the spider hole 210 may be a through hole that mayextend through the spider 176. The input shaft 72 may extend through thespider hole 210.

One or more spider shafts 212 may extend away from the first axis 80 andthe spider hole 210. In the configuration shown, three spider shafts 212are provided; however, it is contemplated that a greater or lessernumber of spider shafts 212 may be provided. Each spider shaft 212 mayextend along a spider shaft axis that may be disposed substantiallyperpendicular to the first axis 80. In addition, an end of each spidershaft 212 may be received in a corresponding spider shaft hole 160 ofthe case 22.

Referring to FIGS. 2, 3 and 5, a pinion gear 178 may be rotatablydisposed on a corresponding spider shaft 212. Each pinion gear 178 mayhave teeth that may mesh with teeth on the first side gear 174 and thegear portion 192 of the input gear 170.

Referring to FIGS. 2-4, the interaxle differential unit 26 mayoperatively connect the input shaft 72 and the case 22 to the drivepinion 74 and/or the output shaft 76. The interaxle differential unit 26may compensate for speed differences between different drive axleassemblies, such as speed differences between the axle assembly 10 and asecond axle assembly that is connected in series with the axle assembly10. The interaxle differential unit 26 may include a clutch collar 220,a second side gear 222, a third side gear 224, as well as a spider 176and one or more pinion gears 178. The case 22 may at least partiallyreceive the second side gear 222, third side gear 224, spider 176, andpinion gear(s) 178.

The clutch collar 220, which may also be referred to as a secondcoupling, may be moveably disposed on the drive pinion 74. In addition,the clutch collar 220 may move independently of the first coupling 172.The clutch collar 220 may move axially or move along the first axis 80between a retracted position and an extended position as will bediscussed in more detail below. As is best shown in FIG. 4, the clutchcollar 220 may be generally ring-shaped and may include a clutch collarhole 230, a clutch collar face gear 232, and a clutch collar groove 234.

The clutch collar hole 230 may extend through the clutch collar 220 andextend around the first axis 80. The clutch collar hole 230 may receivethe drive pinion 74 and the third side gear 224. For example, the clutchcollar hole 230 may have a spline that may extend into the clutch collarhole 230 and toward the first axis 80 and may mate with a spline or gearteeth that may be arranged around the circumference of the third sidegear 224. The mating splines may allow the clutch collar 220 to move inan axial direction or along the first axis 80 while inhibiting rotationof the clutch collar 220 about the first axis 80 with respect to thedrive pinion 74 and the third side gear 224.

The clutch collar face gear 232 may include a set of teeth that may facetoward the interaxle differential unit 26. The set of teeth may bearranged around the first axis 80 and may selectively engage the teethof the third case portion face gear 150 depending on the position of theclutch collar 220.

The clutch collar groove 234 may face away from the first axis 80 andmay extend around the first axis 80. The clutch collar groove 234 mayreceive a linkage, such as a shift fork, that may operatively connectthe clutch collar 220 to a second actuator. The second actuator may movethe clutch collar 220 between the unlocked position and the lockedposition. The second actuator may be of any suitable type, such as amechanical, electromechanical, electrical, pneumatic, or hydraulicactuator.

Referring to FIG. 2, the clutch collar face gear 232 may not engage thecase 22 and the third case portion face gear 150 when the clutch collar220 is in the unlocked position. As such, the third side gear 224 anddrive pinion 74 may be permitted to rotate with respect to the case 22.This in turn may allow the case 22 and the output shaft 76 to rotate atdifferent velocities with respect to each other. In addition, the inputshaft 72 and the output shaft 76 may be permitted to rotate at differentvelocities with respect to each other when the clutch collar 220 is inthe unlocked position.

Referring to FIG. 3, the clutch collar face gear 232 may engage thethird side gear 224 when the clutch collar 220 is in the lockedposition, thereby inhibiting the third side gear 224 and the drivepinion 74 from rotating with respect to the case 22. This in turn mayprevent the case 22 and the output shaft 76 from rotating at differentvelocities with respect to each other. In addition, the input shaft 72and the output shaft 76 may be inhibited or prevented from rotating atdifferent velocities with respect to each other when the clutch collar220 is in the locked position.

Referring to FIGS. 2 and 4, second side gear 222 may be fixedly coupledto the output shaft 76. For example, the second side gear 222 may have acenter bore that may receive the output shaft 76. The center bore mayinclude a spline that may mate with a corresponding spline on the outputshaft 76. As such, the second side gear 222 may not rotate about thefirst axis 80 with respect to the output shaft 76.

The third side gear 224 may be fixedly disposed on the drive pinion 74.For example, the third side gear 224 may have a center bore that mayreceive the shaft portion 110 of the drive pinion 74. The center boremay include a spline that may mate with the drive pinion spline 126. Assuch, the third side gear 224 may not rotate about the first axis 80with respect to the drive pinion 74.

The spider 176 of the interaxle differential unit 26 may be fixedlypositioned with respect to the case 22 and may be rotatably disposed onthe output shaft 76. The spider 176 may be spaced apart from the drivepinion 74. As is best shown in FIG. 4, the spider 176 may include aspider hole 210 and one or more spider shafts 212. The output shaft 76may extend through the spider hole 210. The spider shafts 212 of thespider 176 of the interaxle differential unit 26 may be received incorresponding spider shaft holes 162 of the case 22. A pinion gear 178may be rotatably disposed on a corresponding spider shaft 212 of thespider 176. Each pinion gear 178 may have teeth that may mesh with teethon the second side gear 222 and the third side gear 224.

Referring to FIGS. 2 and 4, one or more thrust bearings 142 may bedisposed between the first side gear 174 and the second side gear 222.The thrust bearing 142 may separate the first side gear 174 from thesecond side gear 222 and help axially position the input shaft 72 withrespect to the output shaft 76. For example, a thrust bearing 142 mayextend from the first side gear 174 to the second side gear 222 or thecase 22 may include a divider wall 236 that may be disposed between thefirst side gear 174 to the second side gear 222, in which case a thrustbearing 142 may extend from the first side gear 174 to the divider wall236, a thrust bearing 142 may extend from the second side gear 222 tothe divider wall 236, or both.

Referring to FIG. 2, the differential assembly 28 may be disposed in thecenter portion 50 of the housing assembly 20. The differential assembly28 may transmit torque to the vehicle traction wheel assemblies andpermit the traction wheel assemblies to rotate at different velocities.An abbreviated discussion of the operation of the differential assembly28 follows with reference to FIGS. 1 and 2, beginning with the inputyoke 70 shown in FIG. 1.

The input yoke 70 may be coupled to a vehicle drivetrain component, suchas a drive shaft, that may be coupled to an output of a vehicletransmission or transfer case, which in turn may receive torque from avehicle power source, such as an engine or motor. Alternatively, theinput yoke 70 may be operatively connected to an output of another axleassembly. The input yoke 70 may be operatively connected to the inputshaft 72, which in turn may be operatively connected to the drive pinion74. The drive pinion 74 may provide torque to the ring gear 100 of thedifferential assembly 28. The differential assembly 28 may beoperatively connected to the axle shafts 30 and may permit the axleshafts 30 to rotate at different rotational speeds in a manner known bythose skilled in the art. As such, the differential assembly 28 mayreceive torque via the ring gear 100 and provide torque to the axleshafts 30.

Referring to FIGS. 1 and 2, the axle shafts 30 may transmit torque fromthe differential assembly 28 to corresponding traction wheel assemblies.For example, two axle shafts 30 may be provided such that each axleshaft 30 extends through a different arm portion 52 of axle housing 40.The axle shafts 30 may extend along and may be rotated about the secondaxis 82 by the differential assembly 28. Each axle shaft 30 may have afirst end and a second end. The first end may be operatively connectedto the differential assembly 28. The second end may be disposed oppositethe first end and may be operatively connected to a wheel end assemblythat may have a wheel hub that may support a wheel. As shown in FIG. 1,an axle flange 240 may be disposed proximate the second end of the axleshaft 30 and may facilitate coupling of the axle shaft 30 to the wheelhub.

Referring to FIGS. 6 and 7, a second embodiment is shown in which thegear reduction unit 24′ may include or may be configured as a planetarygear set 250. The planetary gear set 250 may be configured to provide adesired gear reduction ratio and increase torque provided from the inputshaft 72′ to the drive pinion 74 and the output shaft 76, and hence tothe axle shafts 30 of the axle assembly 10 and the second axle assembly.The gear reduction unit 24′ may provide a first drive gear ratio (lowrange drive gear ratio) and a second drive gear ratio (high range drivegear ratio) as previously described. For instance, the first drive gearratio may provide a 3:1 gear reduction ratio or more while the seconddrive gear ratio may provide a 1:1 gear ratio.

The planetary gear set 250 may be disposed in the housing assembly 20.For instance, the planetary gear set 250 may be received in thedifferential carrier 42 and may be axially positioned between an end ofthe differential carrier 42 through which the input shaft 72′ enters thedifferential carrier 42 and the interaxle differential unit 26. In atleast one embodiment, the planetary gear set 250 may include a sun gear260, a plurality of planet pinions 262, a planetary ring gear 264, and aplanet carrier 266.

The sun gear 260 may be disposed proximate the center of the planetarygear set 250 and may be rotatable about the first axis 80. The sun gear260 have a hole that may receive the input shaft 72′ and the firstcoupling 172′. For instance, the first coupling 172′ may be received inthe hole of the sun gear 260 such that the first coupling 172′ may bedisposed between and may separate the input shaft 72′ from the sun gear260. The sun gear 260 may have a sun gear spline 268 that may bedisposed in the hole and that may mate with a corresponding spline onthe first coupling 172′. The mating splines may be configured to permitthe first coupling 172′ to move axially or along the first axis 80 withrespect to the sun gear 260. The sun gear 260 may also have a second setof teeth that may be disposed opposite the hole and that may meshinglyengage or be in meshing engagement with the planet pinions 262.

The planet pinions 262 may be spaced apart from each other and may berotatably disposed between the sun gear 260 and the planetary ring gear264. Each planet pinion 262 may have a planet pinion hole and a set ofteeth. The planet pinion hole may be a through hole that may extendthrough the planet pinion 262. The set of teeth may be disposed oppositethe planet pinion hole. The set of teeth may mesh with teeth on the sungear 260 and teeth on the planetary ring gear 264. Each planet pinion262 may be configured to rotate about a different planet pinion axis.The planet pinion axes may extend substantially parallel to the firstaxis 80.

The planetary ring gear 264 may extend around the first axis 80 and mayreceive the planet pinions 262. The planetary ring gear 264 may includea plurality of teeth that may extend toward the first axis 80 and maymesh with teeth on the planet pinions 262. The planetary ring gear 264may be fixedly positioned with respect to the housing assembly 20 andthe first axis 80. For example, the planetary ring gear 264 may befixedly disposed in the housing assembly 20 such that an outsidecircumference of the planetary ring gear 264 may be disposed on thedifferential carrier 42.

The planet carrier 266 may be coupled to the planet pinions 262 and maybe rotatable about the first axis 80. The planet carrier 266 may includea case portion 270 and one or more pins 272.

The case portion 270 may be part of the case 22. As such, the caseportion 270 may receive components of the interaxle differential unit26. For example, the case portion 270 may receive the spider 176, piniongears 178, second side gear 222, or combinations thereof. The caseportion 270 may be fixedly mounted on another portion of the case 22,such as the third case portion 134. The case portion 270 and the thirdcase portion 134 may cooperate to define one or more spider shaft holes162 that may receive spider shafts 212 of the spider 176 of theinteraxle differential unit 26. An optional thrust bearing 142 may bedisposed between the second side gear 222 and the case portion 270 toaxially position the output shaft 76 with respect to the planet carrier266. In the section views throughout the application, some spider shafts212 are not visible and the lower spider shaft that is visible appearsto have an elongated parabolic or curved configuration due to therotational position of the spider 176 with respect to the section plane.Although the spider 176 is illustrated with three spider shafts 212, itis to be understood that a greater or lesser number of spider shafts 212may be provided.

The case portion 270 may also include a case portion hole 274. The caseportion hole 274 may extend around the first axis 80 and may beconfigured as a through hole that may extend through the case portion270. A case portion spline 276 may be disposed in the case portion hole274 and may have teeth that may extend toward the first axis 80. Thecase portion spline 276 may be spaced apart from the input shaft 72′ andmay be configured to selectively mate with a second coupling spline ofthe first coupling 172′ as will be discussed in more detail below.

One or more pins 272 may extend from the case portion 270 in a directionthat may extend away from the interaxle differential unit 26. Each pin272 may rotatably support a corresponding planet pinion 262.

The first coupling 172′ may be movably disposed on the input shaft 72′.The first coupling 172′ may move axially or in a direction that extendsalong the first axis 80 between a first position and a second position.The first coupling 172′ may include a coupling hole 200′, a firstcoupling spline 202′, a second coupling spline 204′, and a couplinggroove 206′.

The coupling hole 200′ may extend through the first coupling 172′ andmay extend around the first axis 80. The coupling hole 200′ may receivethe input shaft 72′.

The first coupling spline 202′ may extend into the coupling hole 200′and toward the first axis 80. The first coupling spline 202′ may matewith an input shaft spline 210′ that may be disposed on the exterior ofthe input shaft 72′. The mating splines may allow the first coupling172′ to move in an axial direction while inhibiting rotation of thefirst coupling 172′ about the first axis 80 with respect to the inputshaft 72′.

The second coupling spline 204′ may be disposed opposite the firstcoupling spline 202′. As such, the second coupling spline 204′ mayextend away from the first axis 80. The second coupling spline 204′ mayhave an axial length that may be less than an axial length of the firstcoupling spline 202′ so that the second coupling spline 204′ cannotsimultaneously mesh with the sun gear spline 268 and the case portionspline 276.

The coupling groove 206′ may face away from the first axis 80 and mayextend around the first axis 80. The coupling groove 206′ may receive alinkage, such as a shift fork, that may operatively connect the firstcoupling 172′ to the first actuator 208. The first actuator 208 may movethe first coupling 172′ between the first position and the secondposition.

Referring to FIG. 6, the second coupling spline 204′ of the firstcoupling 172′ may mate with the sun gear spline 268 when the firstcoupling 172 is in the first position. As such, the sun gear 260 mayrotate with the input shaft 72′ about the first axis 80 while the planetpinions 262 and the planet carrier 266 (and hence the case 22) mayrotate with respect to the sun gear 260. Accordingly, torque may betransmitted from the input shaft 72′ to the sun gear 260 and then to theplanet carrier 266 via the planet pinions 262, thereby allowing theplanetary gear set 250 to provide gear reduction associated with thefirst drive gear ratio.

Referring to FIG. 7, the second coupling spline 204′ may mate with thecase portion spline 276 when the first coupling 172′ is disposed in thesecond position. As such, the planet carrier 266 may rotate with theinput shaft 72′ about the first axis 80 and torque may be transmittedfrom the input shaft 72′ directly to the planet carrier 266 rather thanvia the sun gear 260 and the planet pinions 262.

Referring to FIGS. 8 and 9, a third embodiment is shown in which thegear reduction unit 24″ may include or may be configured as a planetarygear set 350 that may provide a desired gear reduction ratio. In thisconfiguration, the planetary gear set 350 may include a sun gear 360, aplurality of planet pinions 362, a planetary ring gear 364, and a planetcarrier 366.

The sun gear 360 may be disposed proximate the center of the planetarygear set 350 and may be rotatable about the first axis 80. Morespecifically, the sun gear 360 may be fixedly positioned with respect tothe input shaft 72 such that the sun gear 360 may not rotate about thefirst axis 80 with respect to the input shaft 72. The sun gear 360 maybe secured to the input shaft 72 in any suitable manner, such as withmating splines, snap rings or other fasteners, welding or combinationsthereof. The sun gear 360 may have teeth that may extend away from thefirst axis 80 that may meshingly engage the planet pinions 362.

The planet pinions 362 may be spaced apart from each other and may berotatably disposed between the sun gear 360 and the planetary ring gear364. The planet pinions 362 may have the same configuration or a similarconfiguration as the planet pinions 262.

The planetary ring gear 364 may extend around the first axis 80 and mayreceive the planet pinions 362. The planetary ring gear 364 may includea plurality of teeth that may extend toward the first axis 80 and maymesh with teeth on the planet pinions 362. The planetary ring gear 264may be movable with respect to the housing assembly 20 and the firstaxis 80. For example, the planetary ring gear 264 may be actuated by thefirst actuator 208 and may move axially or in a direction that extendsalong the first axis 80 between a first position and a second positionas will be discussed in more detail below. The planetary ring gear 364may also include a first planetary ring gear face gear 380 and a secondplanetary ring gear face gear 382.

The first planetary ring gear face gear 380 may include a set of teeththat may face away from the case 22. The set of teeth may be arrangedaround the first axis 80 and may selectively engage the teeth of thehousing face gear 56 of the differential carrier 42 depending on theposition of the planetary ring gear 364.

The second planetary ring gear face gear 382 may be disposed oppositethe first planetary ring gear face gear 380. The second planetary ringgear face gear 382 may include a set of teeth that may face toward thecase 22. The set of teeth may be arranged around the first axis 80 andmay selectively engage the teeth of a planet carrier face gear 374depending on the position of the planetary ring gear 364 as will bedescribed in more detail below.

The planet carrier 366 may be coupled to the planet pinions 362 and maybe rotatable about the first axis 80. The planet carrier 366 may includea case portion 370 one or more pins 372, and a planet carrier face gear374.

The case portion 370 may be part of the case 22. As such, the caseportion 370 may receive components of the interaxle differential unit26. The case portion 370 may be fixedly mounted on another portion ofthe case 22, such as the third case portion 134. The case portion 370and the third case portion 134 may cooperate to define one or morespider shaft holes 162 that may receive spider shafts 212 of the spider176 of the interaxle differential unit 26. An optional thrust bearing142 may be disposed between the second side gear 222 and the caseportion 370 to axially position the output shaft 76 with respect to theplanet carrier 366.

One or more pins 372 may extend from the case portion 370 in a directionthat may extend away from the interaxle differential unit 26. Each pin372 may rotatably support a corresponding planet pinion 362, similar tothe pins 272 previously discussed.

The planet carrier face gear 374 may be disposed on a side of the caseportion 370 that may face away from the interaxle differential unit 26.The planet carrier face gear 374 may be the same as or similar to thefirst case portion face gear 140. As such, the planet carrier face gear374 may include a plurality of teeth that may be arranged around thefirst axis 80. The teeth may extend toward the planetary ring gear 364.

Referring to FIG. 8, the first planetary ring gear face gear 380 of theplanetary ring gear 364 may mate with the housing face gear 56 and maybe disengaged from the planet carrier face gear 374 when the planetaryring gear 364 is in the first position. As such, the sun gear 360 mayrotate with the input shaft 72 about the first axis 80 while the planetpinions 362 and the planet carrier 366 (and hence the case 22) mayrotate with respect to the sun gear 360. Accordingly, torque may betransmitted from the input shaft 72 to the sun gear 360 and then to theplanet carrier 366 via the planet pinions 362, thereby allowing theplanetary gear set 350 to provide gear reduction associated with thefirst drive gear ratio.

Referring to FIG. 9, the second planetary ring gear face gear 382 maymate with the planet carrier face gear 374 and may be disengaged fromthe housing face gear 56 when the planetary ring gear 364 is in thesecond position. As such, the planetary ring gear 364 may not rotatewith respect to the planet carrier 366, which in turn may inhibitrotation of the planet pinions 362 and the sun gear 360, an input shaft72 with respect to the case 22.

Referring to FIGS. 10 and 11, a fourth embodiment is shown in which thegear reduction unit 24′ may include or may be configured as a planetarygear set 450. This embodiment is similar to the embodiment shown inFIGS. 8 and 9 in that planetary gear set 450 may include may include asun gear 360, a plurality of planet pinions 362, a planetary ring gear364′, and a planet carrier 366 and the planetary ring gear 364′ may movealong the first axis 80. However, the planetary ring gear 364′ may omitthe first planetary ring gear face gear, a first actuator 208′ mayactuate the planetary ring gear 364′ to the first position, and one ormore biasing members 460 may actuate the planetary ring gear 364′ to thesecond position.

The first actuator 208′ may be configured as a clutch pack, anelectromagnetic clutch, or hydraulically actuated clutch. Activation oractuation of the first actuator 208′ may move the planetary ring gear364′ to the first position as is best shown in FIG. 10, therebydisengaging the planetary ring gear 364′ from the planet carrier 366 andcoupling the planetary ring gear 364′ to the housing assembly 20.

One or more biasing members 460 may bias the planetary ring gear 364′toward the second position. The biasing member 460 may be of anysuitable type. For example, the biasing member 460 may be configured asa wave washer, spring, or the like. As is best shown in FIG. 11, thebiasing member 460 may be disposed between the housing assembly 20 andthe planetary ring gear 364′ and may urge or actuate the planetary ringgear 364′ to the second position when sufficient force is not exerted bythe first actuator 208′.

Referring to FIGS. 12 and 13, another configuration of an axle assemblyis shown. This configuration may include a housing assembly 20, a case22, a gear reduction unit 24, an interaxle differential unit 26, adifferential assembly 28, and at least one axle shaft 30, an input yoke70, an input shaft 72, and an output yoke 78 as previously discussed. Inaddition, the axle assembly may include an output shaft 500, a drivegear 502, a driven gear 504, a drive pinion 506, and a clutch collar508.

The output shaft 500 may be similar to the output shaft 76′ previouslydescribed. As such, the output shaft 500 may extend along and may beconfigured to rotate about the first axis 80, may be rotatably supportedby one or more roller bearings, may extend through the spider 176 of theinteraxle differential unit 26, may be fixedly coupled to the secondside gear 222 of the interaxle differential unit 26 at a first end, andmay be fixedly coupled to the output yoke 78 at a second end. In thisconfiguration, the output shaft 500 may not extend through a drivepinion, but instead may be disposed in or may extend through the drivegear 502. In addition, the output shaft 500 may have an output shaftspline 510. The output shaft spline 510 may include a plurality of teeththat may be disposed substantially parallel to the first axis 80 and maymate with a corresponding spline on the clutch collar 508.

The drive gear 502 may be operatively connected to the interaxledifferential unit 26. For example, the drive gear 502 may receive torquefrom the third side gear 224 of the interaxle differential unit 26. Inat least one configuration, the drive gear 502 may have a center borethrough which the output shaft 500 may extend. In addition, the drivegear 502 may include a drive gear portion 520, a first hub 522, and asecond hub 524.

The drive gear portion 520 may include a plurality of teeth that may bedisposed opposite the center bore. The teeth of the drive gear portion520 may mesh with teeth of the driven gear 504.

The first hub 522 may extend axially from the drive gear portion 520.For example, the first hub 522 may extend axially toward the interaxledifferential unit 26. The first hub 522 may at least partially definethe center bore and may be fixedly coupled to the third side gear 224 ofthe interaxle differential unit 26. For instance, the first hub 522 mayinclude a first hub spline 530 that may be received in the third sidegear 224 and that may mate with a corresponding spline of the third sidegear 224. As such, the third side gear 224 may be inhibited fromrotating with respect to the drive gear 502. The first hub 522 may alsofacilitate mounting of the drive gear 502. For example, the first hub522 may be received in a roller bearing assembly 532 that may be mountedto the differential carrier 42. The roller bearing assembly 532 may beaxially positioned between the drive gear portion 520 and the first hubspline 530 and may be disposed outside of the case 22 in one or moreconfigurations.

The second hub 524 may extend axially from the drive gear portion 520and may be disposed opposite the first hub 522. For example, the secondhub 524 may extend toward the clutch collar 508. The second hub 524 mayat least partially define the center bore and may be selectively engagedby the clutch collar 508. For instance, the second hub 524 may include asecond hub gear 540 that may be selectively engaged by the clutch collar508. The second hub 524 may be received in another roller bearingassembly 532 that may be mounted to the differential carrier 42. Theroller bearing assembly 532 may be axially positioned between the drivegear portion 520 and the second hub gear 540. The second hub gear 540may have teeth that may be arranged around the first axis 80, teeth thatmay extend axially away from the drive gear portion 520, or both

The driven gear 504 may be rotatable about a third axis 550. Inaddition, driven gear 504 may be fixedly disposed with respect to thedrive pinion 506. For example, the driven gear 504 may include a holethat may receive the drive pinion 506 such that the driven gear 504 andthe drive pinion 506 are rotatable together about the third axis 550.The driven gear 504 may include a plurality of teeth that may bearranged around the third axis 550 and that may mesh with teeth of thedrive gear portion 520 of the drive gear 502.

The drive pinion 506 may be rotatable about the third axis 550 and mayprovide torque to the ring gear 100. The drive pinion 506 may berotatably supported by one or more roller bearing assemblies 552 thatmay be disposed on the differential carrier 42. The drive pinion 506 mayinclude a shaft portion 554 and a gear portion 556. The shaft portion554 may extend from the driven gear 504 to the gear portion 556. Thegear portion 556 may be disposed at an end of the shaft portion 554 andmay have a plurality of teeth that may mesh with corresponding teeth onthe ring gear 100.

The clutch collar 508, which may also be referred to as a secondcoupling, may provide similar functionality as the clutch collar 220previously described. The clutch collar 508 may be movable with respectto the output shaft 500 along the first axis 80 between an unlockedposition and a locked position. For example, the clutch collar 508 mayhave a clutch collar hole that may receive the output shaft 500. Aclutch collar spline 560 that may be disposed in the clutch collar holethat may mate with the output shaft spline 510. The mating splines mayallow the clutch collar 508 to move in an axial direction or along thefirst axis 80 while inhibiting rotation of the clutch collar 508 withrespect to the output shaft 500. A clutch collar gear 562 may facilitatecoupling of the clutch collar 508 to the drive gear 502. For example,the clutch collar gear 562 may be selectively engageable with the secondhub gear 540. In FIG. 12, the clutch collar gear 562 is depicted withteeth that are arranged around the first axis 80 and that may extendaround the second hub gear 540; however, it is contemplated that theclutch collar gear 562 may be configured as a face gear that may haveteeth that may extend axially toward the drive gear 502. The clutchcollar 508 may also have a clutch collar groove 234 that may facilitatecoupling of the clutch collar 508 to the second actuator 570 aspreviously described.

In FIG. 12, the clutch collar 508 is disposed in an unlocked position inwhich the clutch collar 508 does not couple the drive gear 502 to theoutput shaft 500. As such, the output shaft 500 may rotate at adifferent velocity with respect to the third side gear 224 and the drivegear 502. In addition, the input shaft 72 and the output shaft 500 maybe permitted to rotate at different velocities with respect to eachother when the clutch collar 508 is in the unlocked position.

In FIG. 13, the clutch collar 508 is disposed in a locked position inwhich the clutch collar 508 couples the drive gear 502 to the outputshaft 500. As such, the output shaft 500, third side gear 224, and thedrive gear 502 may rotate together about the first axis 80. In addition,the input shaft 72 and the output shaft 500 may be inhibited orprevented from rotating at different velocities with respect to eachother when the clutch collar 508 is in the locked position.

Referring to FIGS. 14-25, additional configurations of gear reductionunits that may include or may be configured as a planetary gear set areshown. These configurations may be employed with axle assemblies inwhich the output shaft extends through a drive pinion, such as is shownin FIG. 2 or with an axle assembly configuration in which the outputshaft does not extend through a drive pinion, such as is shown in FIG.12. It is also contemplated that double planetary gear sets may beprovided with any of the gear reduction units having a planetary gearsets described herein.

Referring to FIGS. 14-16, a gear reduction unit is shown that may haveplanet pinions 262, a planetary ring gear 264, and planet carrier 266 aspreviously described. The gear reduction unit may also include a sungear 600, a planet carrier ring 602, and a first coupling 604.

The sun gear 600 may be disposed proximate the center of the planetarygear set and may be rotatable about the first axis 80. The sun gear 600have a hole that may receive the input shaft 72′. The sun gear 600 mayhave teeth that may mesh with the planet pinions 262 and may have a gear610 that may be selectively coupled to the first coupling 604. Morespecifically, the gear 610 may be a face gear that may have a pluralityof teeth that may be arranged around the first axis 80 and that mayextend in an axial direction away from the case 22.

The planet carrier ring 602, which may also be referred to as an outerplanet carrier, may extend around the first axis 80 and the sun gear600. The planet carrier ring 602 may be fixedly disposed on the planetcarrier 266. For example, the planet carrier ring 602 may be fixedlydisposed on the pins 272 of the planet carrier 266. The planet carrierring 602 may have a set of planet carrier ring teeth 612 that may bearranged around the first axis 80 and that may extend toward the firstcoupling 604. The planet carrier ring teeth 612 may be disposed closerto the first axis 80 than the pins 272.

The first coupling 604, which may also be referred to as a first collar,may be movably disposed on the input shaft 72′. The first coupling 604may have a coupling hole 620, a first coupling spline 622, a secondcoupling spline 624, a coupling gear 626, and a coupling groove 628.

The coupling hole 620 may extend through the first coupling 604 and mayextend around the first axis 80. The coupling hole 620 may receive theinput shaft 72′.

The first coupling spline 622 may extend into the coupling hole 620 andtoward the first axis 80. The first coupling spline 622 may mate withthe input shaft spline 210′. The mating splines may allow the firstcoupling 604 to move in an axial direction while inhibiting rotation ofthe first coupling 604 about the first axis 80 with respect to the inputshaft 72′.

The second coupling spline 624 may be disposed opposite the firstcoupling spline 622. As such, the second coupling spline 624 may extendaway from the first axis 80. The second coupling spline 624 may beselectively engageable with the planet carrier ring teeth 612. Thesecond coupling spline 624 may have an axial length that may be lessthan an axial length of the first coupling spline 622.

The coupling gear 626 may be disposed at an end of the first coupling604 that may face toward the sun gear 600. The coupling gear 626 mayinclude a plurality of teeth that may be arranged around the first axis80. The teeth may be selectively engageable with the gear 610 of the sungear 600.

The coupling groove 628 may have a similar configuration or the sameconfiguration as coupling groove 206′. As such, the coupling groove 628may facilitate coupling of the first coupling 604 to the first actuator208.

In FIG. 14, the first coupling 604 is shown in a neutral position. Inthe neutral position, the first coupling 604 may not couple the inputshaft 72′ to the sun gear 600 or to the planet carrier ring 602.

In FIG. 15, the first coupling 604 is shown in a first position in whichthe first coupling 604 couples the input shaft 72′ to the sun gear 600.For example, the coupling gear 626 may mate with the gear 610 of the sungear 600. As such, the sun gear 600 may rotate with the input shaft 72′about the first axis 80 while the planet pinions 262 and the planetcarrier 266 (and hence the case 22) may rotate with respect to the sungear 600. Accordingly, torque may be transmitted from the input shaft72′ to the sun gear 600 and then to the planet carrier 266 via theplanet pinions 262, thereby allowing the planetary gear set to providegear reduction associated with the first drive gear ratio.

In FIG. 16, the first coupling 604 is shown in a second position inwhich the first coupling 604 couples the input shaft 72′ to the planetcarrier ring 602. For example, the second coupling spline 624 may matewith the planet carrier ring teeth 612. As such, the sun gear 600 may befree to rotate about the first axis 80 with respect to the input shaft72′ while the planet carrier 266 and the input shaft 72′ may rotatetogether about the first axis 80. Accordingly, torque may be transmittedfrom the input shaft 72′ to the planet carrier 266 and the case 22,thereby allowing the planetary gear set to provide gear reductionassociated with the second drive gear ratio.

Referring to FIGS. 17-19, a gear reduction unit is shown that may haveplanet pinions 262, a planetary ring gear 264, a planet carrier 266, anda planet carrier ring 602 as previously described. This configurationmay differ from that shown in FIGS. 14-16 in configuration of the sungear and the first coupling.

The sun gear 600′ may have the similar configuration as sun gear 600 butmay have a gear 610′ that is not be a face gear. Instead the gear 610′may have an annular hub 630 that may extend from a lateral side of thesun gear 600′ in a direction that extends axially away from the planetcarrier 266. The teeth of the gear 610′ may be arranged around theannular hub 630 and may extend radially away from the first axis 80. Thesun gear 600′ may be fixedly disposed on the input shaft 72′.

The first coupling 604′ may have the same configuration as firstcoupling 604, except that the coupling gear 626′ may not be a face gear.Instead the coupling gear 626′ may be disposed in the coupling hole 620and may have teeth that may be arranged around the first axis 80 andthat may extend radially toward the first axis 80.

In FIG. 17, the first coupling 604′ is shown in a neutral position. Inthe neutral position, the first coupling 604′ may not couple the inputshaft 72′ to the sun gear 600′ or to the planet carrier ring 602.

In FIG. 18, the first coupling 604′ is shown in a first position inwhich the first coupling 604′ couples the input shaft 72′ to the sungear 600′. For example, the coupling gear 626′ may mate with the gear610′ of the sun gear 600′. As such, the sun gear 600′ may rotate withthe input shaft 72′ about the first axis 80 while the planet pinions 262and the planet carrier 266 (and hence the case 22) may rotate withrespect to the sun gear 600′. Accordingly, torque may be transmittedfrom the input shaft 72′ to the sun gear 600′ and then to the planetcarrier 266 via the planet pinions 262, thereby allowing the planetarygear set to provide gear reduction associated with the first drive gearratio.

In FIG. 19, the first coupling 604′ is shown in a second position inwhich the first coupling 604′ couples the input shaft 72′ to the planetcarrier ring 602. For example, the second coupling spline 624 may matewith the planet carrier ring teeth 612. As such, the sun gear 600′ maybe free to rotate about the first axis 80 with respect to the inputshaft 72′ while the planet carrier 266 and the input shaft 72′ mayrotate together about the first axis 80. Accordingly, torque may betransmitted from the input shaft 72′ to the planet carrier 266 and thecase 22, thereby allowing the planetary gear set to provide gearreduction associated with the second drive gear ratio.

Referring to FIGS. 20-22, a gear reduction unit is shown that may have asun gear 360, planet pinions 362, and a planet carrier 366 as previouslydescribed. The gear reduction unit may also include a planetary ringgear 700, a support flange 702, a planet carrier ring 704, and a firstcoupling 706.

The planetary ring gear 700 may extend around the first axis 80 and mayreceive the planet pinions 362. The planetary ring gear 700 may includea plurality of teeth that may extend toward the first axis 80 and maymesh with teeth on the planet pinions 362. The planetary ring gear 700may be rotatable with respect to the housing assembly 20 and the firstaxis 80. As such, the planetary ring gear 700 may be spaced apart fromthe housing assembly 20. Unlike the configuration shown in FIGS. 8-11,the planetary ring gear 700 may not move axially along the first axis80.

The support flange 702 may be fixedly disposed with respect to theplanetary ring gear 700. The support flange 702 may be provided as aseparate component from the planetary ring gear 700 or may be integrallyformed with the planetary ring gear 700. The support flange 702 mayextend around the first axis 80 and may receive the first coupling 706.In addition, the support flange 702 may be disposed on a side of theplanetary ring gear 700 that is disposed opposite the case 22. In atleast one configuration, the support flange 702 may include an outerwall 710, an intermediate wall 712, and an inner wall 714.

The outer wall 710 may extend from the planetary ring gear 700. Theouter wall 710 may be radially disposed with respect to the first axis80.

The intermediate wall 712 may extend from an end of the outer wall 710to an end of the inner wall 714. Moreover, the inner wall 714 may bedisposed substantially perpendicular to the first axis 80 in one or moreconfigurations. The intermediate wall 712 may be axially positionedbetween the planet carrier 366 and a support 720 that may extend fromthe differential carrier 42.

The inner wall 714 may extend from the intermediate wall 712. The innerwall 714 may be radially disposed with respect to the first axis 80. Inaddition, the inner wall 714 may be disposed closer to the first axis 80than the outer wall 710. The inner wall 714 may receive the firstcoupling 706 and may include a set of support flange teeth 730 that maybe arranged around the first axis 80 and that may extend toward thefirst coupling 706. The support flange teeth 730 may be disposed closerto the first axis 80 than the pins 372 of the planet carrier 366. One ormore roller bearing assemblies 732 may be disposed on a side of theinner wall 714 that may be disposed opposite the support flange teeth730. The roller bearing assemblies 732 may rotatably support the supportflange 702. In at least one configuration, one or more roller bearingassembly 732 may extend from the inner wall 714 to the support 720 ofthe differential carrier 42.

The planet carrier ring 704, which may also be referred to as an outerplanet carrier, may extend around the first axis 80 and the input shaft72. The planet carrier ring 704 may be fixedly disposed on the planetcarrier 366. For example, the planet carrier ring 704 may be fixedlydisposed on the pins 372 of the planet carrier 366. The planet carrierring 704 may have a set of planet carrier ring teeth 740 that may bearranged around the first axis 80 and that may extend toward the firstcoupling 706. The planet carrier ring teeth 740 may be disposed closerto the first axis 80 than the pins 372.

The first coupling 706, which may also be referred to as a first collar,may be movable along the first axis 80. The first coupling 706 may havea coupling hole 750, a coupling gear 752, a coupling spline 754, and acoupling groove 756.

The coupling hole 750 may extend through the first coupling 706 and mayextend around the first axis 80. The coupling hole 750 may receive andmay be spaced apart from the input shaft 72.

The coupling gear 752 may be disposed at an end of the first coupling706 that is disposed opposite the case 22. The coupling gear 752 mayhave a set of teeth that may be arranged around the first axis 80 andthat may extend in an axial direction away from the case 22.

The coupling spline 754 may be disposed opposite the coupling hole 750.As such, the coupling spline 754 may have teeth that may extend awayfrom the first axis 80. The coupling spline 754 may mate with thesupport flange teeth 730 of the support flange 702. In addition, thecoupling spline 754 may selectively mate with the planet carrier ringteeth 740 of the planet carrier ring 704.

The coupling groove 756 may have a similar configuration or the sameconfiguration as coupling groove 206′. As such, the coupling groove 756may facilitate coupling of the first coupling 706 to the first actuator208.

In FIG. 20, the first coupling 706 is shown in a neutral position. Inthe neutral position, the first coupling 706 may not couple theplanetary ring gear 700 to the case 22 or the planet carrier 366.

In FIG. 21, the first coupling 706 is shown in a first position in whichthe first coupling 706 couples the planetary ring gear 700 to the case22. For example, the coupling gear 752 may mate with the housing facegear 56. As such, the planetary ring gear 700 may not rotate about thefirst axis 80 with respect to the housing assembly 20 and the planetpinions 362 may be rotatable with respect to the sun gear 360.Accordingly, torque may be transmitted from the input shaft 72 to thesun gear 360, planet pinions 362 and to the planet carrier 366 (andhence the case 22), thereby allowing the planetary gear set to providegear reduction associated with the first drive gear ratio.

In FIG. 22, the first coupling 706 is shown in a second position inwhich the first coupling 706 couples the planetary ring gear 700 to theplanet carrier 366. For example, the coupling spline 754 may mate withthe planet carrier ring teeth 740 of the planet carrier 366. As such,the planetary ring gear 700 may not rotate with respect to the planetcarrier 366 and the planet pinions 362 may not rotate with respect tothe planet carrier 366 and the planetary ring gear 700. Thus, the sungear 360, planet carrier 366, and the planetary ring gear 700 may rotatetogether about the first axis 80. Accordingly, torque may be transmittedfrom the input shaft 72 to the case 22, thereby allowing the planetarygear set to provide gear reduction associated with the second drive gearratio.

Referring to FIGS. 23-25, a gear reduction unit is shown that may haveplanet pinions 362, a planet carrier 366, a planetary ring gear 700, anda support flange 702 as previously described. The gear reduction unitmay also include a sun gear 800 and a first coupling 802.

The sun gear 800 may be fixedly positioned with respect to the inputshaft 72. The sun gear 800 may be integrally formed with the input shaft72 or may be provided as a separate component. The sun gear 800 may haveteeth that may mesh with teeth of the planet pinions 362 as previouslydescribed. In addition, a gear 810 may be provided with the sun gear800, the input shaft 72, or both that may be selectively coupled to thefirst coupling 802. For example, the gear 810 may be a face gear thatmay have a plurality of teeth that may be arranged around the first axis80 and that may extend in an axial direction away from the case 22.

The first coupling 802 may be movable along the first axis 80. The firstcoupling 802 may have a coupling hole 850, a first coupling gear 852, acoupling spline 854, a coupling groove 856, and a second coupling gear858.

The coupling hole 850 may extend through the first coupling 802 and mayextend around the first axis 80. The coupling hole 850 may receive andmay be spaced apart from the input shaft 72.

The first coupling gear 852 may be disposed at an end of the firstcoupling 802 that is disposed opposite the case 22. The first couplinggear 852 may have a set of teeth that may be arranged around the firstaxis 80 and that may extend in an axial direction away from the case 22.

The coupling spline 854 may be disposed opposite the coupling hole 850.As such, the coupling spline 854 may have teeth that may extend awayfrom the first axis 80. The coupling spline 854 may mate with thesupport flange teeth 730 of the support flange 702. In addition, thecoupling spline 854 may selectively mate with the gear 810.

The coupling groove 856 may have a similar configuration or the sameconfiguration as coupling groove 756. As such, the coupling groove 856may facilitate coupling of the first coupling 802 to the first actuator208.

The second coupling gear 858 may be disposed at an end of the firstcoupling 802 that is disposed opposite the first coupling gear 852. Thesecond coupling gear 858 may have a set of teeth that may be arrangedaround the first axis 80 and that may extend radially toward the firstaxis 80.

In FIG. 23, the first coupling 802 is shown in a neutral position. Inthe neutral position, the first coupling 802 may not couple theplanetary ring gear 700 to the case 22, the input shaft 72, or the sungear 800.

In FIG. 24, the first coupling 802 is shown in a first position in whichthe first coupling 802 couples the planetary ring gear 700 to the case22. For example, the first coupling gear 852 may mate with the housingface gear 56. As such, the planetary ring gear 700 may not rotate aboutthe first axis 80 with respect to the housing assembly 20 and the planetpinions 362 may be rotatable with respect to the sun gear 800.Accordingly, torque may be transmitted from the input shaft 72 to thesun gear 800, planet pinions 362, and to the planet carrier 366 (andhence the case 22), thereby allowing the planetary gear set to providegear reduction associated with the first drive gear ratio.

In FIG. 25, the first coupling 802 is shown in a second position inwhich the first coupling 802 couples the planetary ring gear 700 to thegear 810. For example, the second coupling gear 858 may mate with thegear 810. As such, the planetary ring gear 700 may not rotate withrespect to the input shaft 72 and the sun gear 800. Consequently, theplanet pinions 362 may not rotate with respect to the planet carrier 366and the planetary ring gear 700. Thus, the sun gear 800, planet carrier366, and the planetary ring gear 700 may rotate together about the firstaxis 80. Accordingly, torque may be transmitted from the input shaft 72to the case 22, thereby allowing the planetary gear set to provide gearreduction associated with the second drive gear ratio.

The axle assembly configurations described above may allow an axleassembly to provide faster drive gear ratios, which may reduce the peaktorque requirements of other drivetrain components, such as thetransmission and driveshafts, which in turn may reduce the cost andweight of these components. Components of the gear reduction unit andthe interaxle differential unit may be commonized and may be disposed inthe same case in the arrangements that employ spiders, which may reducecomplexity and package space. Configurations in which the gear reductionunit employs a planetary gear set may also reduce package space and mayprovide a greater range of gear reduction ratios.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. An axle assembly comprising: a housing assembly that receives a differential assembly; an input shaft that is rotatable about a first axis and is at least partially received in the housing assembly; a gear reduction unit that is disposed in the housing assembly and is operatively connected to the input shaft, wherein the gear reduction unit includes a planetary gear set that has a sun gear that is rotatable about the first axis, a planet carrier that rotatably supports a planet pinion, and a ring gear that is fixedly positioned with respect to the housing assembly; and a first coupling that is moveable between a first position in which the first coupling couples the input shaft to the sun gear such that the sun gear and input shaft are rotatable together about the first axis and a second position in which the first coupling couples the input shaft to the planet carrier such that the planet carrier and the input shaft are rotatable together about the first axis; and an interaxle differential unit that is received in a case that is at least partially defined by the planet carrier and that operatively connects the planetary gear set to the differential assembly and an output shaft.
 2. The axle assembly of claim 1 wherein the input shaft extends through the first coupling and the first coupling and input shaft are rotatable together about the first axis.
 3. The axle assembly of claim 1 wherein the first coupling does not rotate with respect to the sun gear when disposed in the first position and does not rotate with respect to the planet carrier when disposed in the second position.
 4. The axle assembly of claim 1 wherein the output shaft is operatively connected to the interaxle differential unit and rotatable about the first axis, wherein the gear reduction unit provides gear reduction from the input shaft to the output shaft and the differential assembly when the first coupling is in the first position and the gear reduction unit does not provide gear reduction from the input shaft to the output shaft and the differential assembly when the first coupling is in the second position.
 5. The axle assembly of claim 1 wherein the first coupling moves away from the interaxle differential unit when the first coupling moves from the first position to the second position.
 6. The axle assembly of claim 1 wherein the first coupling moves toward the interaxle differential unit when the first coupling moves from the first position to the second position.
 7. The axle assembly of claim 1 further comprising a drive gear that is rotatable about the first axis and is operatively connected to the interaxle differential unit, a driven gear that meshes with the drive gear and is rotatable about a third axis, and a drive pinion that is rotatable about the third axis to provides torque to the differential assembly.
 8. The axle assembly of claim 1 further comprising a drive pinion that provides torque to the differential assembly and is rotatable about the first axis and is operatively connected to the interaxle differential unit, and the output shaft that is received in the drive pinion and is rotatable about the first axis, wherein the interaxle differential unit operatively connects the gear reduction unit to the drive pinion and the output shaft.
 9. The axle assembly of claim 8 wherein the drive pinion is rotatable with the output shaft when the interaxle differential unit is locked and the drive pinion is rotatable with respect to the output shaft when the interaxle differential unit is unlocked.
 10. An axle assembly comprising: a housing assembly that receives a differential assembly; an input shaft that is at least partially received in the housing assembly and is rotatable about a first axis; a gear reduction unit that is operatively connected to the input shaft, wherein the gear reduction unit includes a planetary gear set that has a sun gear and a planetary ring gear that are rotatable about the first axis and a planet carrier that rotatably supports a planet pinion that is in meshing engagement with the sun gear and the planetary ring gear, wherein the planetary ring gear is moveable between a first position in which the planetary ring gear is coupled to the housing assembly such that the planetary ring gear does not rotate about the first axis and a second position in which the planetary ring gear is coupled to the planet carrier such that the planet carrier and the planetary ring gear are rotatable together about the first axis; and an interaxle differential unit that is at least partially received in the planet carrier and that operatively connects the planetary gear set to the differential assembly and an output shaft.
 11. The axle assembly of claim 10 wherein the planetary ring gear is moveable along the first axis between the first position, the second position, and a neutral position that is disposed between the first position and the second position, wherein torque is not transmitted from the input shaft to the planet carrier when the planetary ring gear is in the neutral position.
 12. The axle assembly of claim 10 wherein the planetary gear set provides gear reduction from the input shaft to the output shaft and the differential assembly when the planetary ring gear is in the first position.
 13. The axle assembly of claim 12 wherein the planetary gear set does not provide gear reduction from the input shaft to the output shaft and the differential assembly when the planetary ring gear is in the second position.
 14. The axle assembly of claim 10 wherein the planetary ring gear is coupled to the housing assembly and is disengaged from the planet carrier when in the first position and the planetary ring gear is coupled to the planet carrier and is disengaged from the housing assembly when in the second position.
 15. The axle assembly of claim 14 further comprising an actuator that moves the planetary ring gear between the first position and the second position.
 16. The axle assembly of claim 15 wherein the actuator includes a clutch pack that actuates the planetary ring gear to the first position and a biasing member that extends from the housing assembly to the planetary ring gear that actuates the planetary ring gear to the second position.
 17. An axle assembly comprising: a housing assembly that receives a differential assembly; an input shaft that is at least partially received in the housing assembly and is rotatable about a first axis; a gear reduction unit that is operatively connected to the input shaft, wherein the gear reduction unit includes a planetary gear set that has a sun gear and a planetary ring gear that are rotatable about the first axis and a planet carrier that rotatably supports a planet pinion that is in meshing engagement with the sun gear and the planetary ring gear, wherein the planetary ring gear is selectively rotatable about the first axis; a first coupling that is moveable between a first position in which the planetary ring gear is coupled to the housing assembly such that the planetary ring gear does not rotate about the first axis and a second position in which the planetary ring gear is not coupled to the housing assembly and is rotatable about the first axis; and an interaxle differential unit that is at least partially received in the planet carrier and that operatively connects the planetary gear set to the differential assembly and an output shaft.
 18. The axle assembly of claim 17 wherein the first coupling couples the planetary ring gear to the planet carrier when in the second position such that the planet carrier and the planetary ring gear are rotatable together about the first axis.
 19. The axle assembly of claim 17 wherein the first coupling couples the planetary ring gear to the sun gear when in the second position such that the sun gear and the planetary ring gear are rotatable together about the first axis.
 20. The axle assembly of claim 17 wherein the first coupling is received in a support flange that is fixedly positioned with respect to the planetary ring gear and is moveable along the first axis with respect to the support flange. 